RADIO AND ITS RECEIVERS

Sun (Auckland), Volume III, Issue 837, 4 December 1929, Page 16

RADIO AND ITS RECEIVERS

Conducted for THE SUN Dy R. F. HAYCOCK.

SURPRISES FOR LISTENERS?

HINTS OF TELEVISION LONDON’S NEW STATION What surprises are awaiting listeners—particularly London listeners — when the great new "regional” transmitting station, now rapidly nearing completion a few miles north of London, is put into service? asks a London exchange. Although the regional scheme has been under discussion for more than two years and the present station tinder construction for the greater part of a year, it is still extremely doubtful as to what will be the station's actual effect. This station, which will be known as "Brookman’s Park,” is expected ultimately to replace the present London transmitter. It appears likely that it will adopt the existing callsign—2LO. A remarkable circumstance in connection with the new station is that although the P.M.G.'s licence to the 11.8. C. called for the provision of double machinery to enable transmissions to be carried out on two wavelengths at the same time, the operati rig licence permits only one of these wave-lengths to be used. Why?

A suggestion made in one quarter, t hough not officially, is that the P.M.G. is keeping this second transmitter up his sleeve for possible future use for television transmissions. SPARE STATION

Provided that the forthcoming tests at Brookman’s Park are satisfactory, and the first transmitter is definitely put into service, it is argued, there will be a perfectly good spare station in hand. It is only reasonable to assume that definite developments in television are not far off, and what could be better than to use this spare machine*}' —the latest word in transmitting efficiency—for experiments in the new art, and perhaps for permanent use if such experiments should prove perfectly successful?

"The station at Brookman’s Park will be :*eady for engineers’ tests on

one wave-length in the early summer,” said an official of the 8.8. C. to a reporter. "Rumours of the abandonment of the regional scheme are entirely false, and it is expected that the station will be in full use a few weeks later.” HIGH POWER AND SELECTIVITY Considerable doubt exists a 3 to the probable effect of the new station in the London area. The 30 kilowatts of power with which it is to be equipped will undoubtedly render it a very simple matter to receive its transmissions, particularly in North London, but the suggestion is being expressed that this high power will make it practically impossible for anyone not equipped with an extremely selective set ever to receive anything else! Potter’s Bar, where the station is situated, is within 15 miles of the centre of London. Thus a large proportion of listeners will find themselves within what may prove to be unpleasantly close range of the new giant. At present there are thousands of persons within a mile or two of 2LO's three kilowatts who find it a sufficiently difficult matter to eliminate London in favour of any other station on the same wave-band. When, within a few miles, they find a station operating on 10 times the power of the present 2LO, their difficulties will certainly not be decreased!

CHILDREN’S CHOIR

RICHMOND ROAD VISITS IYA Mr. Norman Day, first assistant master at the Richmond Road School, whose pleasant voice has often been heard from IYA, took a choir of children from the school to IYA on Friday evening. The children sang several delightful numbers during the children’s session. The voices blended well and gave evidence of careful training. Not only is Mr. Day an excellent singer himself, but he knows how to get the best out of children, and more should be heard of his choir from Richmond Road.

WIRELESS LICENCES

INCREASE IN AUSTRALIA Figures have been made available showing the licences issued in each State of Australia to the end of October, 1929, and the following shows the increases which have taken place during the last 12 months: Oct., Oct., Increase 1928. 1929. 1 Year. New South Wales 88,983 107,509 15,526 Victoria 141,988 144,295 2,307 Queensland .. .. 25,484 23,487 *1,997 South Australia 21,436 24,737 3,301 West Australia. • 3,844 4,353 509 Tasmania .. .. 3.524, 5,441 1,617 Commonwealth . 255.549 309,822 24,273 •Decrease. ■Every State, excepting Queensland, shows an increase, New South Wales leading with nearly 80 per cent, of the total. Now West Australia has come under the . national broadcasting scheme there has been, in two months, an increase of 4.15 licences, the greatest increase in that State since .1925, when licences reached 3,943 and practically remained stationary for four years until the inauguration of the new service. Queensland has been going back slowly and the present licences in force, 23,487, are less than the number existing as far back as 1927.

SCREEN-GRID VALVES 816 HOUR CONTINUOUS TEST Determined to find out lor themselves how good the Atwater Kent screen-grid is, Park and Hull, Baltimore distributors, put a model on test on a service bench on May 21. The valves were selected at random from the regular stock and tested carefully. The set was then turned to station W.C.A.O. All controls were turned on full and the' set was left to its fate. It was not touched for an entire month, as originally planned. In fact, it was allowed to run four more days lor good measure, Sl6 hours in all. It was still functioning perfectly. The valves were then tested again. All gave a good account of themselves.Some tested better than when new. The screen-grid valves were best of all.

HIGH TENSION VOLTAGE

The importance of providing and maintaining an adequate high-tension battery voltage on valve receivers is often over-looked by listeners. It will be found in many cases that when using a single high-tension battery unit having a pressure of 45 volts or 60 volts, sufficient volume can be obtained from many wireless receivers to fill a large room. From this it is argued that the battery pressure provided is adequate for the normal operation of the receiver. As a matter of fact, although the volume obtained from the set may be all that is required, it will be found by the critical listener that the quality of reproduction will be far from satisfactory. A few years ago, when a single type of valve was used for all purposes in receiving, a pressure of about 60 volts from the high-tension battery was usually sufficient to operate the valve normally. These valves, however, were electrically incapable of producing a sufficient volume of undistorted sound for really effective loudspeaker operation, and since they were almost invariably overloaded to the extent of giving a more or less badly distorted output, the extra distortion due to insufficient high-tension battery pressure was seldom noticeable. In all but the cheapest of modern receivers, provision is made for the employment of power valves. When power valves are fitted they should always he supplied with sufficient hightension pressure for their normal operation. 11l no circumstances should a high-tension pressure of less than 100 volts be employed. In most cases, it will be found highly advantageous to increase the pressure on the last amplifying valve in the receiver ! to about 150 volts.